The total amount of light emitted by a light source, or radiant flux, is never fully perceived by an observer results in a difference between the actual brightness of light being emitted and a perceived brightness. The reduced perceived brightness is due to a number of factors. First, the human eye has varying levels of sensitivity depending on the wavelength(s) of light that are perceived. However, another reason for reduced perceived brightness is a biological phenomenon referred to as physioneural compression.
The eye of an observer comprises thousands of photoreceptor cells, including rod cells and cone cells. Furthermore, there are three types of cone cells, namely long, medium, and short. Each type of cone cells is more responsive to different ranges of wavelengths of light. Long cone cells have a peak responsiveness around 564-580 nanometers, medium cone cells around 534-545 nanometers, and short cone cells around 420-440 nanometers. Physioneural compression occurs when light is incident upon the cone cells and includes two or more wavelengths of light that generate responses in two or more types of cone cells. When this occurs, physioneural cells, which are in communication with the cone cells, are forced to integrate the visual information into a signal to be transmitted to the visual cortex of the brain, which then further interprets the visual information and causes the observer to have a coherent understanding of the visual information. When physioneural cells interpret information from more than one type of cone cell at a time, it reduces the perceived brightness of the sum of the visual information received.
For example, if long cone cells are providing visual information with a normalized brightness of one unit, and short cone cells are also providing visual information with a normalized brightness of one unit, the physioneural cells transmit that visual information to the visual cortex with a brightness of less than one unit. This is how present lighting devices operate. Accordingly, there is a need for a lighting device that emits light in such a way as to avoid physioneural compression, thereby increasing the perceived brightness of the light.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.